bpo-41739: Fix test_logging.test_race_between_set_target_and_flush() (GH-22655) (GH-22656) (GH-22662)

The test now waits until all threads complete to avoid leaking
running threads.

Also, use regular threads rather than daemon threads.

(cherry picked from commit 13ff396)
(cherry picked from commit f5393dc)

Co-authored-by: Victor Stinner <[email protected]>

Co-authored-by: Victor Stinner <[email protected]>

Author: miss-islington

Lib/test/test_logging.py

@@ -1177,22 +1177,27 @@ def test_race_between_set_target_and_flush(self):
         class MockRaceConditionHandler:
             def __init__(self, mem_hdlr):
                 self.mem_hdlr = mem_hdlr
+                self.threads = []
 
             def removeTarget(self):
                 self.mem_hdlr.setTarget(None)
 
             def handle(self, msg):
-                t = threading.Thread(target=self.removeTarget)
-                t.daemon = True
-                t.start()
+                thread = threading.Thread(target=self.removeTarget)
+                self.threads.append(thread)
+                thread.start()
 
         target = MockRaceConditionHandler(self.mem_hdlr)
-        self.mem_hdlr.setTarget(target)
+        try:
+            self.mem_hdlr.setTarget(target)
 
-        for _ in range(10):
-            time.sleep(0.005)
-            self.mem_logger.info("not flushed")
-            self.mem_logger.warning("flushed")
+            for _ in range(10):
+                time.sleep(0.005)
+                self.mem_logger.info("not flushed")
+                self.mem_logger.warning("flushed")
+        finally:
+            for thread in target.threads:
+                support.join_thread(thread)
 
 
 class ExceptionFormatter(logging.Formatter):

Misc/NEWS.d/next/Tests/2020-10-12-00-11-47.bpo-41739.wSCc4K.rst

@@ -0,0 +1,2 @@
+Fix test_logging.test_race_between_set_target_and_flush(): the test now
+waits until all threads complete to avoid leaking running threads.